Fluorescent tube lamps are gas-discharge lamps. When a discharge occurs between electrodes of a fluorescent tube due to a voltage exceeding a certain threshold, a short is created from one electrode to the other and current rapidly rises. If the current is not controlled, the fluorescent tube can break.
Henceforth, fluorescent tube mounts are provided with a ballast which has the function of providing a satisfactory form of electric power to correctly drive the fluorescent tubes therein. Two of the most common forms of ballasts are magnetic ballasts and electronic ballasts. Magnetic ballasts were used for many decades. The most common forms of magnetic ballast are the lead-lag circuit and the series sequence circuit which can be used to simultaneously drive two fluorescent tubes held in corresponding sockets of a multiple fluorescent tube mount. The lead-lag circuit allows to offset the intermittent activation of the fluorescent tubes (each running at ˜50-60 Hz) by 180° in a manner to give the eye a lighting at ˜100-120 Hz and thus reduce the potentially stroboscopic effect.
In recent years electronic ballasts have tended to replace magnetic ballasts. Electronic ballast build up a high amount of voltage typically faster than magnetic ballasts (typically in less than 1 ms) and can thus lead to more instantaneous illumination. Moreover, independent electronic ballasts are typically provided for corresponding fluorescent tubes. Notwithstanding the above, dual magnetic ballasts are still widely present, especially in older constructions.
In even more recent years, Light Emitting Diodes (LEDs) lamps have received an increasing amount of attention, especially given the fact that their lighting efficiency and power consumption are now considered to compete with fluorescent tube lighting. There is thus an increased motivation for providing a LED lamp product which could simply replace a fluorescent tube on existing ballasts.
Although such LED lamp products have been provided which were satisfactory to a certain degree, there remained room for improvement. Particularly in addressing the issues specific to making the LED lamp adaptable to dual magnetic ballasts.